1. Field of the Invention
This invention provides an improved process for cis-1-{2-[4-(6-methoxy-2-phenyl-1,2,3,4-tetrahydronaphthalen-1-yl)phenoxy]ethyl}pyrrolidine which is an intermediate for the preparation of (xe2x88x92)cis-6-phenyl-5-[4-(2-pyrrolidin-1-yl-ethoxy)-phenyl]-5,6,7,8-tetrahydronaphthalene-2-ol which is useful for the treatment of osteoporosis.
2. Description of the Related Art
A preparation of (xe2x88x92)cis-6-phenyl-5-[4-(2-pyrrolidin-1-yl-ethoxy)-phenyl]-5,6,7,8-tetrahydronaphthhalene-2-ol is described in U.S. Pat. No. 5,552,241 which is hereby incorporated by reference. This compound is an estrogen agonist and is useful for treatment of conditions caused by estrogen difficiency. U.S. Pat. No. 5,552,241 also describes the synthesis of cis-1-{2-[4-(6-methoxy-2-phenyl-1,2,3,4-tetrahydronaphthalen-1-yl)phenoxy]ethyl}pyrrolidine by hydrogeneration of nafoxidine.
Lednicer, et al., J. Med. Chem., 12, 881 (1969) described estrogen antagonists of the structure 
wherein R2 is phenyl or cyclopentyl and R3 is H, 
or xe2x80x94CH2CHOHCH2OH.
Bencze, et al., J. Med. Chem., 10, 138 (1967) prepared a series of tetrahydronaphthalenes intended to achieve separation of estrogenic, antifertility and hypocholesterolemic activities. These structures are the general formula 
wherein R1 is H or OCH3; R2 is H, OH, OCH3, OPO(OC2H5)2, OCH2CH2N(C2H5)2, OCH2COOH or OCH(CH3) COOH.
U.S. Pat. No. 3,234,090 refers to compounds which have estrogenic and antifungal properties of the formula 
in which Ph is a 1,2-phenylene radical, Ar is a monocyclic carbocyclic aryl group substituted by tertiary amino-lower alkyl-oxy, in which tertiary amino is separated from oxy by at least two carbon atoms, R is hydrogen, an aliphatic radical, a carbocyclic aryl radical, a carbocyclic aryl-aliphatic radical, a heterocyclic aryl radical or a heterocyclic aryl aliphatic radical, the group of the formula xe2x80x94(CnH2n-2)xe2x80x94 stands for an unbranched alkylene radical having from three to five carbon atoms and carrying the groups Ar and R, salts, N-oxides, salts of N-oxides or quaternary ammonium compounds thereof, as well as procedure for the preparation of such compounds.
U.S. Pat. No. 3,277,106 refers to basic ethers with estrogenic, hypocholesterolemic and antifertility effects which are of the formula 
in which Ph is a 1,2-phenylene radical, Ar is a monocyclic aryl radical substituted by at least one amino-lower alkyl-oxy group in which the nitrogen atom is separated from the oxygen atom by at least two carbon atoms, R is an aryl radical, and the portion xe2x80x94(CnH2n-2)xe2x80x94 stands for lower alkylene forming with Ph a sixxe2x80x94 or seven-membered ring, two of the ring carbon atoms thereof carry the groups Ar and R, salts, N-oxides, salts of N-oxides and quaternary ammonium compounds thereof.
Lednicer, et al., in J. Med. Chem. 10, 78 (1967) and in U.S. Pat. No. 3,274,213 refer to compounds of the formula 
wherein R1 and R2 are selected from the class consisting of lower alkyl and lower alkyl linked together to form a 5 to 7 ring member saturated heterocyclic radical. References
1. Kanapure, S. P.; Das, K. G.; Bhawal, B. M. Synth. Comm. 1984, 14, 1205-1211.
2. Lexa, D.; Saveant, J. M.; Zickler, J. J. Amer. Chem. Soc. 1977, 99, 2786-2790.
3. Chan, T. H.; Brook, M. A.; Chaly, T. Synthesis 1983, 203-205.
4. Gedye, R.; Smith, F.; Westaway, K.; Ali, H.; Baldisera, L.; Laberge, L.; Rousell, J. Tet. Lett. 1986, 27, 279-282.
5. McMurry, J. E.; Kees, K. L. J. Org. Chem. 1977, 42, 2655-2656.
This invention provides intermediate compounds which are useful for the preparation of (xe2x88x92)cis-6-phenyl-5-[4-(2-pyrrolidin-1-yl-ethoxy)-phenyl]-5,6,7,8-tetrahydronaphthalene-2-ol. These compounds include: 3-(2-Bromo-5-methoxy-phenyl)-1-phenyl-propan-1-one; 2-[2-(2-Bromo-5-methoxy-phenyl)-ethyl]-2-phenyl-[1,3]dioxolane; 3-[2-(4-Benzyloxy-benzoyl)-5-methoxy-phenyl]-1-phenyl-propan-1-one; and 4-(4-Benzyloxy-phenyl)-7-methoxy-3-phenyl-1,2-dihydro-naphthalene; and (4-Benzyloxy-phenyl)-({4-methoxy-2-[2-(2-phenyl-[1,3]dioxolan-2-yl)-ethyl]-phenyl }-methanone.
This invention also provides a method of preparing Cis-1-{4-[6-methoxy-2-phenyl-1,2,3,4-tetrahydronaphthalene-1-yl)phenoxy]ethyl}pyrrolidine which comprises the following steps:
1) 2-Bromo-5-methoxy-toluene is brominated to provide 1-bromo-2-bromomethyl-4-methoxybenzene;
2) The product of step 1 is used to alkylate benzoyl acetate ethyl ester followed by decarboxylation to provide 3-(2-bromo-5-methoxyphenyl)-1-phenyl-propan-1-one;
3) The product of step 2 is reacted with ethylene glycol to produce 2-[2-(2-bromo-5-methoxyphenyl)-ethyl]-2-phenyl)-ethyl]-2-phenyl-[1,3]dioxolane;
4) The product of step 3 undergoes metal-halogen exchange with n-butyl lithium and is reacted with 4-benzyloxy benzonitrile to produce 2-[2-(2-(4-benzyloxybenzoyl)-5-methoxy phenyl)-ethyl]-2-phenyl-[1,3]-dioxolane which is subjected to acid hydrolysis of the 1,3 dioxolane to provide 3-[2-(4-benzyloxy-benzoyl)-5-methoxyphenyl]-1-phenyl propan-1-one;
5) The product of step 4 is treated with titanium (III) chloride and zinc-copper couple to produce 4-(4-benzyloxyphenyl)-7-methoxy-3-phenyl-1,2-dihydronaphthalene;
6) The product of step 5 is hydrogenated and treated with triphenyl phosphine, DEAD and 1-(2-hydroxyethyl)pyrolidine to produce 1-{2-[4-(6-methoxy-2-phenyl-1,2,3,4-tetrahydronaphthalene-1-yl)-ethyl}-pyrolidine.
This invention also provides a method of reacting 
to produce 
wherein R is a protected phenol or 
which comprises reacting 2-[2-(2-bromo-5-methoxy-phenyl)-ethyl]-2-phenyl-[1,3]dioxolane with butyl lithium followed by reaction with 
This invention provides a new synthesis of cis-1-{2-[4-(6-methoxy-2-phenyl-1,2,3,4-tetrahydronaphthalen-1-yl)phenoxy]ethyl}pyrrolidine as shown below.
Acronyms used in this description are defined as follows:
The term xe2x80x9cprotected phenolxe2x80x9d includes optional benzyloxy groups substituted with alkoxy, nitro or halogen, and other acceptable alcohol protecting groups.

The synthesis begins with bromination1 of 2-bromo-5-methoxy-toluene to provide the benzyl bromide 1-Bromo-2-bromomethyl-4-methoxy-benzene. Alkylation of ethyl benzoylacetate2 with the benzyl bromide followed by decarboxylation leads to the ketone 3-(2-Bromo-5-methoxy-phenyl)-1-phenyl-propan-1-one, which is protected3 as the ketal 2-[2-Bromo-5-methoxy-phenyl)-2-phenyl-[1,3]dioxolane. Metal-halogen exchange of ketal 2-[2-Bromo-5-methoxy-phenyl)-2-phenyl-[1,3]dioxolane provides an aryl-lithium species, which adds readily to either 4-benzyloxy-benzoate or 4-benzoxy-benzontrile4 and furnishes the diketone 3-[2-(4-Benzyloxy-benzoyl)-5-methoxy-phenyl]-1-phenyl-propan-1-one upon acidic work-up. The diketone undergoes a titanium mediated McMurry type coupling5 to provide the alkene 4-(4-Benzyloxy-phenyl)-7-methoxy-3-phenyl-1,2-dihydro-naphthalene, which possesses the carbon framework of cis-1-{2-[4-(6-methoxy-2-phenyl-1,2,3,4-tetrahydronaphthalen-1-yl)phenoxy]ethyl}pyrrolidine with all the functional groups in place. A palladium catalyzed hydrogenation achieves the reduction of the olefinic double bond and deprotection of the benzyl ether in one pot. The introduction of the N-ethyl-pyrrolidino side-chain is achieved under Mitsunobu conditions to afford 1-{2-[4-(6-Methoxy-2-phenyl-1,2,3,4-tetrahydro-naphthalen-1-yl)-phenoxy]-ethyl}-pyrrolidine, the key precursor to cis-1-{2-[4-(6-methoxy-2-phenyl-1,2,3,4-tetrahydronaphthalen-1-yl)phenoxy]ethyl}pyrrolidine. This compound is converted to cis-6-phenyl-5-[4-(2-pyrrolidin-1-yl-ethoxy)-phenyl]-5,6,7,8-tetrahydronaphthalene-2-ol with HBr as described in U.S. Pat. No. 5,552,241.